How can a busy freshman start acting with no experience?

Hi everyone. I am a high school freshman interested in exploring acting. I love singing, voice mimicry, and comedy, but I have never performed before. I feel comfortable trying to perform around my peers, though I can be shy around adults.

Unfortunately, my school’s competitive drama auditions have already passed. And given my heavy workload which includes AP classes and year-round competitive swimming my schedule is tight. While I am highly creative, I am also balancing a long-term career interest in becoming an oncology Physician Assistant, but still have some hopes of getting into a acting career because I believe I would enjoy that more.

Given my lack of experience and heavy commitments, how can I safely test the waters with acting? Should I focus strictly on school and swimming right now, or is there a manageable way to try acting on the side but still try and turn it into something more than just an on the side thing?